Sanding device



Jan. 28, 1936. p KRAMER E AL 2,028,874 I SANDING DEVICE Filed uarch 16,1934 INVENTORS.

ATTORNEYS.

l mented Jan. 28, 1936 UNHTQEQ aceasvi sannnvc nsvrcn Application March18, 1934, Serial No. 715,797 ill Claims. (Ci. 51-195) This inventionrelatesto devices for sanding surfaces of various coats of finishingmaterial applied to objects such as automobile bodies, and moreespecially to disks sor pads employed in ,5 such devices. i

The principal object of the invention is to incprove the art ofsmoothing and finishing the surface of an object.

Another object is to provide a power device of 1c the above characterwhich effectively smooths the surface of a finishing material by cuttingdown such material to the level of the depressions therein rather thanmerely grinding or eroding the material by cutting down the low spots orin depression as well as the high spots.

a further object is to prevent excessive rolling of a mobile abrasivecomposition and rendering the latter relatively fixed with respect tothe working surface of a sanding device to effect a shearing so actionin addition to an eroding or grinding action.

It is a further object to provide a power device for cutting down theso-called jorange peel surface in lacquer or under coats without materially scratching the same.

Other objects, features and advantages will,

become apparent from the following description and appended claims. v

In finishing the surface oi an object such as oil a metallic body of anautomobile or the like, it is customary to clean the object so thatfinishing materials will more or less permanently adhere thereto andthen apply primer and surfacer coats, or primer-surfacer coats, acombination of the 35 above coats, which coats are used to fill surfacedefects in the obi ct as well as to improve the adhesion of finishingcoats of material such as enamel or lacquer to the object to befinished. The undercoats do-not dry with a smooth, plan ular surface butrather present a rough appearance and some orange peel effects common tothe majority of lacquers. It is necessary to cut down the surfaces ofsuch materials to a plane substantially at the level with the base ofthe eepest depressions therein. It has been the usual practice to cutdown the surfacer coat with sand paper by manual operation. To reducethe labor involved it'is desirable to employ a mechanical devicewherever possible. The mechanical. devices which have been introduced toaccomplish this cutting operation have been either of the rotating wheelor reciprocating type, both employ ing water or other liquid as acooling and lubricating medium. The reciprocal type of device 55 usuallyincludes two flat members each covered with a strip of sand paper andreclprocated by compressed air to simulate the effect of manuallysanding. In this type of device a sander light enough to be easilyhandled has too short a. stroke to effect good results, and in deviceswhere the 5 stroke has been lengthened, the device becomes heavy,unwieldy, noisy, and not easily adapted to curved or irregular surfaces.The power driven rotating wheel type of sanding device is consid erablylighter and more flexible in operation. The latter devices normallyemploy a disk of sand paper, backed by a disk of sponge rubber, orsimilar material, or employ fixed abrasive disks which consists of amixture of rubber or other binder and 90 per cent or more of abrasive,or multiple layers of fabric on which are imposed layers of abrasive andbinder. The majority of these disks v are hard and flexible.

None of the above power devices is adapted for use on any but fiatsurfaces, so that in sanding an object such as an automobile body butapproximately 50 per cent of the surface may be smoothed by such devicesand the remainder must be done manually. In sanding certain types ofunder coats, these devices have been employed with some degree ofsuccess on fiat surfaces only. Care must be taken, however, asthesedevices easily gouge the surface if incorrectly applied thereto or ifallowed to strike a protuberant part such as a hinge, or the like, anick is produced in such part, and it sand paper is used as the cuttingdisk, the latter is torn and must be replaced.

Other attempts have been made to finish under coats by employing therotating wheel type of 5 sander in conjunction with various types ofpads and a mobile abrasive composition. While this device has beenemployed with a considerable degree of success on finish coats, none ofthe pads has proved successful on under coats for any considerablelength of time. Too soft a pad fails to cut down the orange peel due torolling of the abrasive with respect to'the surface of the pad, and toohard a pad will not cut down the orange peel surface without producingtoo deep scratches. Pads of the proper degree of hard ness while cuttingfairly well at the start wear out too quickly to prove practical. Forpads of this type various materials such as felt, leather, rubber,sponge rubber with various covers, carpeting, canvas belting, steelwool, sheep skin, have been tried.

The present invention contemplates the provision of a pad adapted to beemployed on a'rotating wheel and in conjunction with a mobile abrasivecomposition, the pad being of such composition and design that ashearing action is produced in addition to an eroding or grinding actionso that orange peel effects may be removed without excessivelyscratching or gouging the surfaces treated. The device is alsoapplicable to curved as well as fiat surfaces.

For the purpose of illustrating the genus 'of the invention, a. typicalconcrete embodiment thereof is shown in the accompanying drawing, inwhich:

Figure 1 is a cross-section of a finishing or polishing tool or heademploying a sanding pad constructed in accordance with the principles ofthis invention;

Fig. 2 is an enlarged front elevation of the sanding pad shown in Fig.1;

Fig. 3 is a section taken on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged section taken on the line 4-4 of Fig. 2; and

Fig. 5 is a front elevation of a modified form of sanding pad. v

Referring particularly to Fig. l of the drawing, an automobile bodyportion H! has disposed thereon a suitable coating of surfacing materialII, which when dried presents surface irregularities which must be cutdown in order to present a smooth or planular surface. In order toremove such irregularities, the surface of the coating material H iscovered with a suitable water base or oil base abrasive composition andthe latter moved at high speed along the surface under the influence ofa suitable power device to shear 1 face of coating material II by arotating head 12 of a polishing or finishing tool l3. This tool may bedriven directly, by any suitable source of power as, for example, anelectric motor, or may be driven by a flexible shaft M extending from aremote source of power through flexible conduit l5 and having its endthreaded as indicated at 16 into a flanged sleeve I! by which the head12 is rotated. The end of the flexible conduit l5 adjacent the head l2extends into and is rigidly secured to a tubular member I8 by which thehead may be held manually in any desired position during operation ofthe device.

The head 12 comprises a relatively fixed, although flexible disk 20secured to the flanged end 2| of the sleeve H by rivets 22 and a largerconcentric flexible disk 23 which is secured removably to the head by arelatively flat headed stud bolt- 24 projecting through axial openingsin the disk and therebeyond in a centrally disposed opening in the endof the sleeve l1.

Reference may now be had to Figs. 2, 3, and 4 in which the disk 23 isshown as having radially disposed corrugations 25 spaced by similarlydisposed depressions 26 extending from the central portion of the diskto a point spaced from the peripheral margin thereof The corrugationsand depressions are thus both arranged perpendicular to the line ofmotion of various parts of the working face of the disk 23. This disk ispreferably constructed of a medium hard felt, or similar material, andthe depressions are formed by placing the disk in a suitable press.After corrugating the working surface of the disk this face is treatedwith one or more coats of lacquer, primer or similar waterproofing andbinding medium 30 to render the working surface hard and nonabsorbent.This renders the form of the working face of the disk durable and ofpermanent form.

The peripheral edge 3| of the disk 23 is beveled to remove any cornersof the felt to prevent gouging or other injuries to the surface H to betreated.

As will be indicated in Fig. 4 of the drawing, the top surfaces of thecorrugation 25 are of slightly rounded contour and the working surfaceof the disk as impregnated by the lacquer or binding coating 30 is stillrough enough to carry the abrasive composition along the coatingmaterial during rotation of the head [2. This causes the abrasivecomposition to shear off projections or high spots of the surface of thecoating material H Without materially grinding or eroding such surfaceby rolling the abrading composition between the disk 23 and the-coatingmaterial ll. disk 23 is sufiiciently .yieldable so thatobjectionablydeep scratches are not produced. Such scratches areproduced may be a y removed by polishing with a sheep skin or lamb skinpad or disk. The impregnating coating 30 renders thezgw'orking surfaceofflthe disk follow the depressionswithinthe surface of the coatingmaterial I I and do not cause the abrasive composition to be rolledtherethrough so as to wear away the depressions as well as thehighspots. The provisionof depressions 26 between the corrugations 25interrupts any rolling action of the abrasive composition so that but aslight amount of grinding or eroding of the surface of the coatingmaterial ll results. The head l2 of the polishing or finishing tool ispreferably rotated at a speed of from 850 to 1100 revolutions perminute. While the working surface of the disk 23 is hardened by theimpregnating composition 36, it is noted that the flexibility of thedisk is not materially changed. so that in conjunction with therelatively thick flexible backing disk 20 the sanding device may beemployed for polishing curved as well as flat surfaces as indicated inFig. 1.

Referencemay now be had to Fig. 5 of the drawing in which a modifiedform of sanding pad 33 is shown. This pad is also composed of a mediumhard felt, or similar material, and has corrugations 35 spaced by curveddepressions 35 extending generally in a substantially radial directionfrom the central portion of the pad to points spaced trom the peripheryof the pad. This pad is adapted to be rotated in the direction indicatedby the arrow, counterclockwise as viewed in Fig. 5. A surfacing andhardening coating of lacquer, primer or other waterproofing and. bindingmaterial is applied to the work ing surface as in the previousembodiment. The depressions 36 in the outer or peripheral portion of thepad extend or curve somewhat toward the direction of rotation so as tocarry an abrasive composition along the working surface and partiallyprevent the abrasive from being thrown centrifugally from the peripheryof the pad. The functions of the corrugations and depressions areotherwise the same as in the previously described embodiments.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could beeffected without departing from the spirit thereof, it is intended thatall matter containedin the above description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

sufficiently hard so that. parts thereof do not.

What is claimed is:

1. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a pad composed of an inert material,means for moving said pad in a predetermined direction, said pad beingprovided with spaced depressions pressed into its working surface andextending in a direction substantially normal to the direction of motionof said pad, and a binding material, impregnating the working surface ofthe pad to maintain the form thereof.

2. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a pad composed of a medium hardfelt, means for moving said pad in a predetermined direction,corrugations formed on the working surface of said pad with thedepressions thereof extending in a direction normal to the direction ofmovement of said pad, and a coating material impregnating the workingsurface for hardening and maintaining such surface in corrugated form.

3. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a disk-like pad, and means forrotating said pad, said pad being provided with corrugations on itsworking surface and arranged substantially radially of said disk-likepad, said corrugations terminating inwardly of the periphery of saidpad.

4. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a disk-like medium hard felt pad andmeans for rotating said pad, said pad being provided with substantiallyradially disposed depressions pressed into its working surface andterminating short of the periphery of said pad.

5. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a disk-like pad, means for rotatingsaid pad, said pad being provided with spaced depressions pressed intoits working surface and extending in radial directions with respect tothe axis of rotation of said pad, and a binding and waterproofingmaterial impregnating the working surface of said pad to increase thepermanence of the form of said working surface.

6. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a pad composed of a disk-like mediumhard felt, means for rotating said pad, said pad being provided withspaced depressions pressed into its working surface and extending insubstantially radial directions with respect to the axis of rotation ofsaid pad, and a coating material impregnating the working surface ofsaid pad for increasing the permanence of form of said working surface.

7. A sanding device adapted to be employed in conjunction with a mobileabrasive composition and comprising a pad composed of a disk-like mediumhard felt, means for rotating said pad, corrugations formed on theworking surface of said pad with the depressions thereof extending inradial directions with respect to the axis of rotation of said pad, anda coating material impregnating the working surface of said pad forhardening and maintaining such surface in corrugated form.

8. A tool adapted for use in conjunction with a mobile abrasivecomposition for removing surface irregularities from an applied coatingmaterial comprising a disk composed of a medium hard felt and havingsufficient flexibility to follow the general surface contour of saidcoating material, said disk being provided with spaced and radiallydisposed corrugations on the working surface thereof, a hardeningmaterial impregnating the working surface of said disk for preventingthe latter from following the surface irregularities in the appliedcoating material, a flexible and rotatable backing disk, and means forsecuring said first disk on one surface of said backing disk forrotating the felt disk.

9. A tool adapted for use in conjunction with a mobile abrasivecomposition for removing surface irregularities from an applied coatingmaterial comprising a driven shaft, a reinforcing disk of relativelythick but flexible and resilient material secured to the shaft andhaving a substantial marginal portion free for resilient flexing, a diskcomposed of a medium hard felt arranged on the exposed surface of saidreinforcing disk and having a substantial marginal portion projectingbeyond the marginal edge of the reinforcing disk, the working surface ofsaid felt disk being provided with spaced depressions pressed thereinand arranged in generally radial relation with respect to the axis ofrotation of said disk, and a hardening material impregnating the workingsurface of said felt disk for increasing the permanence of form of saidworkingsurface.

10. A sanding device adapted to be employed in conjunction with a mobileabrasive and comprising a disk-like pad, means for rotating the pad inone direction, said pad being provided with corrugations on its workingsurface arranged in a generally radial direction and having the portionsthereof adjacent the periphery of the pad inclined toward the directionof rotation of the pad.

11. A sanding device adapted to be employed in conjunction with a mobileabrasive and comprising a disk-like medium hard felt pad and means forrotating said pad in one direction, said pad being provided with curveddepressions pressed into its working face and extending in generallyradial directions with the portions thereof adjacent the periphery ofthe pad curved toward the direction of rotation of the pad.

PAUL H. KRAMER. JESSE C. THOMPSON.

